10-14-2012 05:07 PM - edited 03-07-2019 09:27 AM
Hi everybody
I am reading about how to configure cisco router as dhcp server and troublshoot any issue related to it
I performed this lab as shown below:
R1--f0/0-199.199.19.0--R2---198.198.198.0----R4
R1 is configured as dhcp client
R2 is dhcp relay agent
R4 is dhcp server.
R1 f0/0 mac address: c000.211c.0000
Below is dhcp ack sent by R4( dhcp server) to R2( relay agent):
No. Time Source Destination Protocol Length Info
760 2618.315000 198.198.198.4 199.199.199.2 DHCP 342 DHCP ACK - Transaction ID 0x1208
Frame 760: 342 bytes on wire (2736 bits), 342 bytes captured (2736 bits)
Ethernet II, Src: c0:03:21:1c:00:00 (c0:03:21:1c:00:00), Dst: c0:01:21:1c:00:10 (c0:01:21:1c:00:10)
Internet Protocol Version 4, Src: 198.198.198.4 (198.198.198.4), Dst: 199.199.199.2 (199.199.199.2)
User Datagram Protocol, Src Port: bootps (67), Dst Port: bootps (67)
Bootstrap Protocol
Message type: Boot Reply (2)
Hardware type: Ethernet
Hardware address length: 6
Hops: 0
Transaction ID: 0x00001208
Seconds elapsed: 0
Bootp flags: 0x8000 (Broadcast)
Client IP address: 0.0.0.0 (0.0.0.0)
Your (client) IP address: 199.199.199.1 (199.199.199.1)
Next server IP address: 0.0.0.0 (0.0.0.0)
Relay agent IP address: 199.199.199.2 (199.199.199.2)
Client MAC address: c0:00:21:1c:00:00 (c0:00:21:1c:00:00)
Client hardware address padding: 00000000000000000000
Server host name not given
Boot file name not given
Magic cookie: DHCP
Option: (t=53,l=1) DHCP Message Type = DHCP ACK
Option: (t=54,l=4) DHCP Server Identifier = 198.198.198.4
Option: (t=51,l=4) IP Address Lease Time = 1 day
Option: (t=58,l=4) Renewal Time Value = 12 hours
Option: (t=59,l=4) Rebinding Time Value = 21 hours
Option: (t=12,l=13) Host Name = "R1.lab.local."
Option: (t=1,l=4) Subnet Mask = 255.255.255.0
End Option
Padding
Above we can see R1 f0/0 is being assigned 199.199.199.1. Lets confirm it.
R1#show ip int brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 199.199.199.1 YES DHCP up up
Now When I check the dhcp binding at R4, I should have found 199.199.199.1----> c0:00:21:1c:00:00 ( R1 f0/0 mac address)
However, I found something completely different:
R4#show ip dhcp binding
Bindings from all pools not associated with VRF:
IP address Client-ID/ Lease expiration Type
Hardware address/
User name
199.199.199.1 0063.6973.636f.2d63. Mar 02 2002 12:57 AM Automatic
3030.302e.3231.3163.
2e30.3030.302d.4661.
302f.30
None of the highlighted mac address matches the R1 f0/0 mac c0:00:21:1c:00:00
What is the issue here?
why do we have more than one mac bind to 199.199.199.1?
Where do these mac addresses come from?
thanks and have a great day.
Solved! Go to Solution.
10-14-2012 05:25 PM
Hello Sarah,
please try this command
R4#show ip dhcp binding 199.199.199.1 and see what is the output.
thanks
10-14-2012 07:36 PM
hello Sarah,
its look like its default server automatic behaviour.
if you do
# debug ip dhcp server packets
it will show you in loggs that 0063.6973.636f.2d63.3030.302e.3266.6130.2e30.3030.302d.4661.302f.30 is one mca adress
R2#
*Oct 24 16:44:19.015: DHCPD: Sending notification of DISCOVER:
*Oct 24 16:44:19.015: DHCPD: htype 1 chaddr 0018.b9cd.bef0
*Oct 24 16:44:19.015: DHCPD: remote id 020a0000ac10170200000000
*Oct 24 16:44:19.015: DHCPD: circuit id 00000000
4 - 15 CCNP: Building Scalable Internetworks v5.0 - Lab 5-5 Copyright 2006, Cisco Systems, Inc
*Oct 24 16:44:19.015: DHCPD: DHCPDISCOVER received from client
0063.6973.636f.2d30.3031.382e.6239.6364.2e62.6566.302d.4661.302f.30 on
interface FastEthernet0/0.
*Oct 24 16:44:19.015: DHCPD: Seeing if there is an internally specified pool
class:
*Oct 24 16:44:19.015: DHCPD: htype 1 chaddr 0018.b9cd.bef0
so in end you will get similar answer.
R2# show ip dhcp binding
Bindings from all pools not associated with VRF:
IP address Client-ID/ Lease expiration Type
Hardware address/
User name
172.16.23.101 0063.6973.636f.2d30. Oct 25 2006 10:20 PM Automatic
3031.382e.6239.6364.
2e62.6566.302d.4661.
302f.30
you can try manual binding if you want hope fully this will bit diffrent.
thanks
10-15-2012 03:51 AM
Hi Sarah,
this string is not the MAC address but the client-identifier.
0063.6973.636f.2d30.3031.382e.6239.6364.2e62.6566.302d.4661.302f.30
is cisco-0018.b9cd.bad0.Fa0/0 in Hex.
You can change this behaviour with the command ip address dhcp client-id fastethernet0/0 and then you'll see the MAC
address of the interface as client-identifier.
Regards.
Alain
Don't forget to rate helpful posts.
10-15-2012 11:02 PM
Hi,
63 in hex is 99 in decimal and the ascii code for decimal 99 is lower case c
69 in hex is 105 in decimal which is ascci code for lowercase i. and so on...
Regards.
Alain
Don't forget to rate helpful posts.
10-17-2012 12:13 AM
Hi Sarah,
http://blog.ioshints.info/2007/08/default-dhcp-client-id.html
Regards.
Alain
Don't forget to rate helpful posts.
10-14-2012 05:25 PM
Hello Sarah,
please try this command
R4#show ip dhcp binding 199.199.199.1 and see what is the output.
thanks
10-14-2012 06:22 PM
Hi Singh
I recreated the lab as shown below, still same result.
R1 f0/0----------f0/0--R2---------------------R3
R1 dhcp client
R2 dhcp relay agent
R3 dhcp server.
R3#show ip dhcp binding 199.199.199.1
IP address Client-ID/ Lease expiration Type
Hardware address/
User name
199.199.199.1 0063.6973.636f.2d63. Mar 02 2002 12:06 AM Automatic
3030.302e.3266.6130.
2e30.3030.302d.4661.
302f.30
R1#show int f0/0
FastEthernet0/0 is up, line protocol is up
Hardware is Gt96k FE, address is c000.2fa0.0000 (bia c000.2fa0.0000)
R1#show ip int brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0/0 199.199.199.1 YES DHCP up up
Thanks
10-14-2012 07:36 PM
hello Sarah,
its look like its default server automatic behaviour.
if you do
# debug ip dhcp server packets
it will show you in loggs that 0063.6973.636f.2d63.3030.302e.3266.6130.2e30.3030.302d.4661.302f.30 is one mca adress
R2#
*Oct 24 16:44:19.015: DHCPD: Sending notification of DISCOVER:
*Oct 24 16:44:19.015: DHCPD: htype 1 chaddr 0018.b9cd.bef0
*Oct 24 16:44:19.015: DHCPD: remote id 020a0000ac10170200000000
*Oct 24 16:44:19.015: DHCPD: circuit id 00000000
4 - 15 CCNP: Building Scalable Internetworks v5.0 - Lab 5-5 Copyright 2006, Cisco Systems, Inc
*Oct 24 16:44:19.015: DHCPD: DHCPDISCOVER received from client
0063.6973.636f.2d30.3031.382e.6239.6364.2e62.6566.302d.4661.302f.30 on
interface FastEthernet0/0.
*Oct 24 16:44:19.015: DHCPD: Seeing if there is an internally specified pool
class:
*Oct 24 16:44:19.015: DHCPD: htype 1 chaddr 0018.b9cd.bef0
so in end you will get similar answer.
R2# show ip dhcp binding
Bindings from all pools not associated with VRF:
IP address Client-ID/ Lease expiration Type
Hardware address/
User name
172.16.23.101 0063.6973.636f.2d30. Oct 25 2006 10:20 PM Automatic
3031.382e.6239.6364.
2e62.6566.302d.4661.
302f.30
you can try manual binding if you want hope fully this will bit diffrent.
thanks
10-15-2012 03:51 AM
Hi Sarah,
this string is not the MAC address but the client-identifier.
0063.6973.636f.2d30.3031.382e.6239.6364.2e62.6566.302d.4661.302f.30
is cisco-0018.b9cd.bad0.Fa0/0 in Hex.
You can change this behaviour with the command ip address dhcp client-id fastethernet0/0 and then you'll see the MAC
address of the interface as client-identifier.
Regards.
Alain
Don't forget to rate helpful posts.
10-15-2012 04:01 PM
Thanks Alain
0063.6973.636f.2d30.3031.382e.6239.6364.2e62.6566.302d.4661.302f.30
is cisco-0018.b9cd.bad0.Fa0/0 in Hex.
The highligted numbers are already in hex
How can we say
0063.6973.636f.2d30.3031.382e.6239.6364.2e62.6566.302d.4661.302f.30
is cisco-0018.b9cd.bad0.Fa0/0 in Hex.?
10-15-2012 11:02 PM
Hi,
63 in hex is 99 in decimal and the ascii code for decimal 99 is lower case c
69 in hex is 105 in decimal which is ascci code for lowercase i. and so on...
Regards.
Alain
Don't forget to rate helpful posts.
10-16-2012 07:55 PM
Hi Alain
0063.6973.636f.2d30.3031.382e.6239.6364.2e62.6566.302d.4661.302f.30
You are saying the above string is in hex, and its ASCI representation is:
cisco-0018.b9cd.bad0.Fa0/0
Is that correct?
But i thought mac address is written in hex.
thanks
10-17-2012 12:13 AM
Hi Sarah,
http://blog.ioshints.info/2007/08/default-dhcp-client-id.html
Regards.
Alain
Don't forget to rate helpful posts.
10-17-2012 02:51 PM
thanks Alain. I got it. Nice link
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